The proposed research is designed to obtain detailed knowledge of the gonadotropin receptor-adenylyl cyclase system of the subhuman primate (monkey) corpus luteum. The specific aims include: (a) characterization of available, occupied and masked receptors for luteinizing hormone (LH) and chorionic gonadotropin (CG) and the LH/CG-sensitive adenylyl cyclase system in macaque luteal tissue; (b) examination of the relationship between gonadotropin receptor-adenylyl cyclase activity and the functional state of the corpus luteum during the normal menstrual cycle; (c) investigation of the in vitro and in vivo effects of potential luteolytic agents, estrogen and prostaglandins, on the gonadotropin receptor-adenylyl cyclase system; and (d) administration of daily injections of increasing doses of chorionic gonadotropin to monkeys to assess changes in gonadotropin receptor-adenylyl cyclase activity in the corpus luteum of simulated early pregnancy. Available and masked gonadotropin receptors will be characterized from the specific binding of 125I-labeled hLH and hCG to macaque luteal particulates before and after exposure to unmasking agents (e.g., ethanol). The number of receptors occupied by endogenous LH or administered hCG will be quantified by indirect (radioimmunoassay of eluted hormone) or direct (125I-hLH binding to treated tissue) methods. Adenyly cyclase activity will be assessed from the conversion of (Alpha 32P) ATP to (Alpha32P) cAMP by luteal homogenates/particulates. The combined objectives are basic to our understanding of the role of the gonadotropin receptor-adenylyl cyclase system in the development, function, and regression of the primate corpus luteum. Moreover, these studies will determine, 1) whether potential luteolytic agents have early, direct effects on the gonadotropin receptor-adenylyl cyclase system of the macaque corpus luteum; and 2) whether early pregnancy in the primate offers a physiologic model for homologous regulation of the gonadotropin receptor-adenylyl cyclase system by chorionic gonadotropin. The investigation will provide new information on the cellular mechanisms regulating the menstrual cycle and early pregnancy, with application to the human condition.